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1.(a) DNA: Genetic information is stored in the order or sequence of nucleotides. Nucleotides code for a polypeptide (a protein) or a RNA molecule (tRNA, rRNA). A genome is all of an organism;s genetic material in a cell. RNA: The “intermediary” molecule in the flow of genetic information. 3 major types of RNA, mRNA(messenger), tRNA(transfer), rRNA(ribosomal). Proteins: Made of strands of amino acids. Types and functions: enzymes (catalyze reactions), structural (support), transport (other molecules), hormones (coordinate cell activities), receptors (respond to and bind chemical stimuli), defense, motor protein, storage (of amino acids)DNA RNA ProteinEncodes Genetic Ifo Yes Yes NoCatalyzes Reactions No Yes YesBuilding Blocks (types)Nucleotides NucleotidesAmino AcidsStrandedness Double Single SingleStructure Double HelixSingle SingleRepair Systems Yes No No (b) Replication: Copies an organisms DNA. The double helix of DNA is unwound and each strand is used as a template for the next. This occurs inside the nucleus. Transcription: The synthesis of mRNA using DNA as a template. This also occurs in the nucleus. Translation: The transcribed mRNA is decoded into a specific protein. This happens at the ribosome in the cytoplasm. (c) Ribosomes are composed of RNA. They are also the site of protein synthesis, where RNA is translated into protein. Two subunits of RNA are used to make the proteins. tRNA is used to carry amino acids in the cytoplasm to help build the polypeptide chain of proteins. Each tRNA attaches to one type of amino acid. (d) The Genetic Code: All organisms use the same genetic code. A codon (triplet of 3 mRNA bases) codes for 1 amino acid. Multiple codons can code for the same amino acid. Your tRNA with the anticodon binds to the mRNA codon. (e) Mutation: A change in the genetic material of a cell. They can be point mutation, a change in one nucleotide, substitution of a nucleotide, or insertions and deletions of anucleotide. These may or may not alter the codon and the amino acid that it would code for. These lead to being “silent”, no amino acid change, “missense”, changes the amino acid, or “nonsense”, which leads to a stop signal and no protein. (f) A gene is a unit of hereditary information.(g) A chromosome is one long double stranded helical DNA molecule. (h) Chromatin is what makes up chromosome. Chromatin is composed of DNA and proteins that bind to DNA. Chromosomes contain euchromatin and heterochromatin. Euchromatin is loosely packed DNA around nucleosomes. It is actively transcribed. Heterochromatin is tightly packed and is genetically inactive, not transcribed. 2. (a) Gene expression, the flow of genetic information, occurs through transcription and translation. Gene regulation is the control of gene expression, i.e. regulating transcription and translation. Some genes have constitutive expression, meaning they’re always on, and some are expressed or repressed as needed in facultative expression. Since all cells have the same genes, it takes regulation of the genes to turn on the right ones needed for the cell. (b) (i) Transcription factors are regulation of gene expression on a gene level, and is the most prevalent form of gene expression. They are regulatory proteins that respond to a signal and bind to specific DNA sequences near a gene in transcription. (ii) Control elements are the DNA sequences upstream of a gene, where you can find transcription factors. Transcription factors bind to the control elements to regulate genes at the initiation of transcription. 3.Type Function ExampleEnzymes Catalyze reactions DNA polymeraseStructural Support Keratin, CollagenTransport Other molecules HemoglobinHormones Coordinate cell/org. activities InsulinReceptors Respond and bind to stimuli G-ProteinsDefense AntibodiesMotor Proteins ActinStorage Of amino acid “reserves” Ovalbumin4. (a) Cells communicate with other cells to decide many things like whether it should divide or not, and so they know what to do to keep the body alive. If there is a specific function that needs to be carried out, it is more efficient to send it to something specific instead of all cells. This is done by cell signaling. (b) Reception: A signal molecule is received by a receptor molecule on the cell membrane or inside the cell. Transduction: A stepwise series of chemical reactions initiated by an activated receptor molecule to elicit a specific cellular response. Response: The end result of a specific signaling pathway. (c) G-Protein linked receptors: Signal pathway using a cell membrane receptor. The receptor activates the G-protein, which then activates the enzyme. Intracellular Receptor: The use of the steroid hormone testosterone (explanation in picture). Multi-step pathway: a Phosphorylation cascade, the transferring of a phosphate group from one to another to reach the target of the original signal. Non- protein “second messenger”: Cyclic amp (cAMP) is activates, and it turn activates a target protein.5.(a) (i) Genomic equivalence: all the different cell types in an organism have identical genomes, but they express different genes. (ii) Our somatic cells are the same because all cells share the same DNA. It is a matter of which genes are expressed that make cells different.(b) (i) Cell potency describes a cells potential to differentiate. (ii) Multipotent: Can differentiate into some, but not all cell types; Adult stem cells. Pluripotent: Can differentiate into any cell type is obtained from a slightly older embryo. Totipotent: Can differentiate into an entire ne individual is obtained from an early embryo. (iii) Stem cells: Relatively undifferentiated cells that be ne induced to be differentiated. (iv) Embryonic stem cells: can be totipotent and pluripotent. Adult stem cells: are multipotent. (v) You can replace damaged tissues and organs by growing them from stem cells.(c) (i) Determination: A process by which a cell differentiates into a particular cell type by expressing a unique set of genes. (ii) Cells can differentiate later in development via induction of cells (one cell signals a neighboring cell to change gene expression.)(iii) Cytoplasmic determinants: Signal molecules that can help regulate gene expression. In early development, the maternal CD’s can regulate early gene expression in embryonic daughter cells either symmetrically or asymmetrically. (d) (i) Cloning: Obtaining an adult asexually from a parent somatic cell.(ii) In


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FSU BSC 2011 - Study Guide

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